The present invention relates to a new and improved construction of a weft thread-selection apparatus for a weaving machine or loom.
Generally speaking, the weft thread-selection apparatus for a weaving machine operates with individual or multiple weft thread insertion and withdraws the filling or weft thread from supply bobbins or spools located externally of the weaving shed. Each weft thread which is to be inserted, prior to its insertion into the shed, is brought by a related weft thread-infeed device of the weft thread-selection apparatus out of a preparatory position into a transfer position serving for the thread transfer to the weft thread-insertion device. The weft thread-infeed device can be connected by means of an electromagnetic control to a to-and-fro driven entrainment device.
Weft thread-selection apparatuses of this type encompass a plurality of adjacently arranged weft thread-infeed devices, each of which guide a weft or filling thread, and which are program-controlled in cycle with the weft thread insertion.
A weft thread-selection apparatus of the aforementioned type is disclosed, for instance, in Swiss Pat. No. 610,367. With this selection apparatus each linearly guided weft thread-infeed device is hingedly connected by means of a connecting rod with one end of a double oscillating or pivotal lever, the other end of which can be selectively fixedly retained or released by an electromagnetically actuatable locking device. An oscillating drive in the form of a cam-driven arm member, which is pivotable or oscillatable about a stationary shaft and engaging at the aforementioned double oscillating lever by means of a bracket member, forces this double oscillating lever to undertake an oscillatory movement. If the locking device is in its locking position then the oscillatory movement is accomplished about the end fixedly retained by the locking device. On the other hand, if the locking device is in its release position then the oscillatory movement is accomplished about the other end of the oscillatory lever which is held in its preparatory position under the action of a spring. Consequently, the selected thread infeed device is only then brought out of the preparatory position into its transfer position when the locking device fixedly retains the one end of the double oscillatory lever.
However, with this prior art construction there prevails the appreciable drawback that it requires numerous components or parts for each weft thread-infeed device as well as thrust armature magnets. Such prior art design of weft thread-selection apparatus therefore is complicated, prone to malfunction or disturbances and expensive. Additionally, this state-of-the-art apparatus requires a timewise exact current infeed and current interruption for the electromagnets in order to accomplish an exact control operation. Also there are needed facilities for exactly maintaining the thread infeed device in its preparatory position, in order to ensure for the latching or locking of the retention locking device.
A weft thread-selection device of the type here under discussion is also known to the art from Swiss Pat. No. 532,671. With this prior art construction a transfer or transmission element connected with the related thread infeed device which is to be actuated is brought by the thrust armature of a related electromagnet into the effective or operative region of a cutter which is continuously moved to-and-fro. By virtue of the effective contact between the transfer or transmission element and the cutter the related thread infeed device moves out of its preparatory position into a transfer position serving for the thread transfer to the weft thread-insertion device. The effective contact between the transfer element and the cutter is ensured for by a spring-loaded pawl element.
Also this heretofore known arrangement contains numerous, and thus, complicated components or parts for each thread infeed device. Additionally, with this prior art construction there are used expensive thrust armature magnets. Although the feature of providing an operative connection between the transfer elements and the cutters avoids the necessity of providing an exact current control for the electromagnets, nonetheless such design still demands an additional high constructional expenditure, and furthermore, is afflicted with the drawback that there is produced an appreciable amount of noise.
In Austrian Pat. No. 257,506 there is disclosed an arrangement containing a transversely travelling slide member and an electromagnetically actuated pawl arrangement. Also this equipment is extremely complicated in its construction and, already for such reason, quite prone to malfunction.
In British Pat. No. 1,467,231 there is disclosed an apparatus containing a lift arrangement supporting a multiplicity of magnets and which moves needles up and down when there is established an appropriate magnetic coupling.